The present invention relates to a winding structure which is applicable to an electromagnetic induction apparatus.
FIG. 1 is a diagrammatic perspective view of a typical example of the prior art winding structure of such an electromagnetic apparatus. As shown, a pair of flat coils 1 and 2 (hereinafter referred to simply as "coils") are wound substantially coaxially with respect to each other. The coils 1 and 2 include winding conductors whose inner ends are connected to each other at a connection P to connect the coils 1 and 2 in series. These coils 1 and 2 further include a plurality of tap leads 3 each of which have one end connected to an intermediate portion of the winding conductor and which extend in a direction intersecting the outer peripheries of the corresponding coils 1 and 2. The outer portions of the coils 1 and 2 including the tap leads 3 are hereinafter referred to as "tap winding portions" (the non-hatched portions in the figure) while the inner portions of the coils 1 and 2 including no tape leads 3 are hereinafter referred to as "main winding portions" (the hatched portions in the figure). The tap winding portions of the coils 1 and 2 are provided with transposition points Q in order to cancel the circulating currents generated in the tap winding portions.
Referring to FIG. 2, which is a circuit diagram of the winding structure shown in FIG. 1, the series-connected coils 1 and 2 each include a plurality of tap leads 3 (in this example, three tap leads for each coil).
FIG. 3 is a diagrammatic side view taken in the direction of an arrow A of FIG. 1. A distance d.sub.1 represents the insulation distance between the tap leads 3 of the coil 1 and the tap leads 3 of the coil 2. A distance d.sub.2 represents the insulation distance between the coil 1 and the tap leads 3 attached thereto and between the coil 2 tap leads 3 attached thereto. A distance d.sub.3 represents the insulation distance between the coils 1 and 2.
FIGS. 4 and 5 illustrate typical examples of the shape of the winding conductor at the transposition points Q of the coils 1 and 2. FIG. 4 shows one example which has no joint area while FIG. 5 shows another example which has a joint.
The tap leads 3 are connected to the winding conductor of the corresponding coil 1 or 2, as shown in FIG. 6.
In the prior art electromagnetic induction apparatus as arranged above, the tap leads 3 are connected directly to the winding conductors of the coil so as to form tap portions. Also, in order to cancel the circulating currents generated in the tap winding portion, at the transposition points Q of the coils 1 and 2, the corresponding winding conductors must be transposed by being twisted 180.degree. about their center lines (shown by the dot-dash line in FIG. 4).
It is to be noted that, although in the example of FIG. 4 there is no joint area, the winding conductors may also have a joint connecting them to each other as shown in FIG. 5.
The prior art electromagnetic induction apparatus having the above-described arrangement includes a winding structure in which the tap leads are connected directly to the winding conductors, as shown in FIG. 6. For this reason, it is necessary to maintain the insulation distances d.sub.2 between the coil 1 and the tap leads 3 attached thereto and between the coil 2 and the tap leads 3 attached thereto, as shown in, for exmaple, FIG. 3. This prior art winding structure has a disadvantage in that this necessity increases the whole size of the electromagnetic induction apparatus. In addition, in order to connect the tap leads to the winding conductors, additional work is required to peel an insulating coating from the portions of the winding conductors to which the tap leads are to be connected. This presents a problem in that in assemblying the electromagnetic induction apparatus is reduced. In addition, as shown in FIGS. 4 and 5, in order to cancel the circulating currents generated in the tap winding portions, transpositions must be effected in the winding portions. This makes it more difficult to form the windings. The prior art electromagnetic induction apparatus involves the above-described problems.